cicada-wifi-hw

IoT Communications Module for Energy Access. A quick way to get production ready, bi-directional communications for your IoT embedded device.

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Cicada-WiFi-HW

Cicada WiFi HW - IoT Communications Module for Energy Access. An easy way to get production ready, bi-directional communications for your IoT embedded device.

This repository contains the hardware design for supported Cicada wifi. This HW is designed to operate with host running cicada-FW. https://github.com/EnAccess/Cicada-FW

Manufacturing files

If you are only interested in manufacturing the PCBs, you only need files in the /manufacturing/ directory. send them to your contract manufacturer of choice,Some examples of other turnkey PCBA manufacturers are:

Manufacturers
JLCPCB
PCBCart
Bittele

you can also get a plug and play module (might require manual FW update) from https://www.seeedstudio.com/Enaccess-Okra-Cicada-Wifi-Communication-PCBA-p-5421.html?queryID=b07d6b6f6e1a3ef37c510602683a5443&objectID=5421&indexName=bazaar_retailer_products.

The /manufacturing/production directory contains the PCB Gerber/drill files, the BOM, and assembly instructions.

Source files

If you'd like to take a look at the schematics and PCB layout, first, make sure you have a fresh version of KiCAD. It's a free and open source electronics design tool, and can be downloaded from http://kicad.org. Make sure you are not using an old version that some Linux distributions might be still shipping.

File structure

The schematics and related files live under the /design/ directory:

Directory	Content
/design/doc/datasheets/	Datasheets for some of the components used. These files are not covered by this project's open source licence
/design/doc/Schematic	Schematics exported as PDF.
/design/source/kicad/	Kicad source files for the CICADA WIFI hardware inculding component lib files and bom generation script
/manufacturing/gerber/	these are set of files which gives information on different layers used in the project (copper layers, silk screen , court yard and other relevent files)
/manufacturing/stackup/	Text file containing the details of the PCB material and stackup
/manufacturing/pick and place/	Pick and place files describing component locations and orientations for PCB Assembly
/manufacturing/nc drill/	NC Drill files describing type and specification of PCB drill holes (vias, through holes, mounting holes etc)
/manufacturing/BOM/	BOM contains the imformation of all the components used in WiFi cicad. directely generated from Kicad using the bom genration script

A quick look at the schematics

The schematics is based on ESP-07S ESP8266 Serial WiFi Module, The module supports standard IEEE802.11 b/g/n agreement, complete TCP/IP protocol stack and capable of +20dBm output power in 802.11b mode. For more information the data sheet of the module will be available in /design/doc/datasheets/ directory

Host interface

The Cicada uses a 2x10 female pin socket that fits perfectly in a 2x8 shrouded pin header on the host side. (We don’t use a 2x8 female pin socket because it is possible to do a off-by-one insertion with it). The host interface provides a way for the host to detect the presence of a Cicada board,transmit and receive data, and distinguish between different Cicada communications boards (Cicada 2g, Cicada 4g):

Pin	Discription
Pin-1 Vref(3v3)	Logic level VCC reference provided by host. only used for VER_1/2 as described below. Other cicadas Vref may be used for level shifiting for I/O pins
Pin-2 VER_1	Board version pin (represents, what type of cicada it is 2g,4g or WiFi), for more information please check schematics
Pin-3 GND
Pin-4 VER_2	Board version pin (represents, latest production release version)
Pin-5 5V	5v Power provided by host. Peak curent consuption <200mA
Pin-6 GND
Pin-7 GND
Pin-8 POWER_EN	Drive high to enable power
Pin-9 NC
Pin-10 NC
Pin-11 NC
Pin-12 UART_Tx_3V3	Should be connected to host's UART_TX
Pin-13 UART_Rx_3V3	Should be connected to host's UART_RX
Pin-14 MODE_SELECT	Pull low to Enable ESP-8266 FW flashing mode,
Pin-15 NC
Pin-16 n_RESET	drive low to reset, drive at 1.8 - 3.3v during normal operation

Power

Board is powered up by single-chip SMPS (HX3406) to convert 5v down to 3.3v required by ESP-07S(ESP8266 Serial WiFi Module WiFi module).

Antenna

The ESP-07S ESP8266 Serial WiFi Module has a on board IPEX connector, which can be extended to an antenna using U.FL cable

ESP8266 operating MODEs

ESP8266 operating MODE	GPIO15	GPIO0	GPIO2
FW flashing	low	low	high
Normal/UART	low	high	high

Need to Flash the module with the latest FW??

Requirements

• USB to serial TTL adapter hardware
• esptool.py (Ubuntu package esptool or GitHub - espressif/esptool: Espressif SoC serial bootloader utility)
• Wifi firmware: https://www.espressif.com/sites/default/files/ap/ESP8266_NonOS_AT_Bin_V1.7.4.zip Note: Make sure the USB to serial adapter is set to 3.3V IO voltage! (usually there is a jumper for that)

Setup

Connect Wifi module and USB adapter

Cicada WiFi	USB adapter
5V0	5V0
GND	GND
POWER_EN	3V3
UART_RX_3V3	Rx
UART_TX_3V3	Tx
MODE_SELECT	GND

The module should now respond to AT commands. You can check this by running the serial_linux example from Cicada.

Flash firmware

• Unzip the firmware package and go to ESP8266_NonOS_AT_Bin_V1.7.4/bin directory. Then run this command to flash: esptool.py -p /dev/ttyUSB0 --chip esp8266 write_flash --flash_size 4MB-c1 0x00000 boot_v1.7.bin 0x01000 at/1024+1024/user1.2048.new.5.bin 0x1fc000 esp_init_data_default_v08.bin 0xfe000 blank.bin 0x1fb000 blank.bin 0x1fe000 blank.bin

After flashing, remove the grounding of IO0(MODE_SELECT) again, so it’s free floating. The Cicada module should now be ready for installation.

Future Improvements

• invitigate on adding an amplifier to the design for range improvemnet